Process for treating red meat to control bacterial contamination and/or growth

ABSTRACT

The surface of red meat is treated with an trialkali metal orthophosphate to reduce, remove, retard or control salmonella, campylobacter, listeria, and spoilage bacteria without causing organoleptic depreciation of the meat, including color change.

The present invention relates to an improved process for reducing thelevel of and retarding the growth of bacteria, on newly slaughtered rawred meat carcasses without causing organoleptic cepreciation thereof.

BACKGROUND OF THE INVENTION

The invention relates to a treatment step made during slaughter of freshmeat and more particularly to treating pork, beef, veal, mutton, lamband goat carcasses with a solution of alkali metal orthophosphate toremove, retard or reduce bacterial contamination and/or growth withoutcausing substantial organoleptic depreciation of the meat.

Red meat, during and after slaughter, may contain or become contaminatedwith certain undesirable bacteria such as salmonella, campylobacter,listeria, spoilage bacteria, and the like. The red meat is process byremoving the hide, eviscerating, cooling and cutting into larger cutsfor fresh, cured meat or boxed meat. The fresh red meat obtained afterevisceration is chilled by hanging the sides of red meat at atemperature usually below 10° C. Beef is hung for a considerable periodto allow natural enzymes to tenderize the beef. Pork is simply cooled.For certain primal cuts, such as ham, bacon, corned beef and pastramithe cuts are cured by chilling below 10° C. followed by injection of asolution containing salt, nitrite and/or nitrate, sweetener, cureaccelerator, one or more polyphosphates, spices and flavorings. The meatis prepared to 105% to 130% of its weight with curing solution. Boxedmeat is cut into primal cuts after chilling, vacuum packaged and boxed.

As disclosed in U.S. Pat. No. 3,782,975 to Zyss, primal cuts of red meatare maintained between 32°-42° F. (for about 3 to 5 days). During thatperiod, the sodium nitrite reacts with the myoglobin of the meat to formnitrosomyoglobin which insures good color to the meat. The addition ofthe curing solution to the primal cuts imparts improved texture,tenderness, flavor and color that would be lacking if the curing brinewas not added to the meat. Zyss teaches that for people with a sodiumproblem, a pumping solution of potassium salts including potassiumorthophosphates could be employed.

A second patent to Zyss, U.S. Pat. No. 3,775,543, suggests the additionof phosphate compositions including potassium orthophosphates toprocessed meats as a binding agent in from 0.2 to 2.0% by weight of themix. Zyss clearly avoids alkaline pH since he indicated that alkaline pHdecreases the meat's shelf life. Zyss neutralizes with acid to pH 6.4 to6.8. In example II, Zyss prepares a bologna product using about 1%tripotassium orthophosphate. Surprisingly, we have found that surfaceorthophosphate treatment increased shelf life.

Ueno, et al. U.S. Pat. No. 4,592,892, uses ethanol to sterilize certainfood and processing machinery and may employ a carbonate and/ortrialkali orthophosphate combined with the ethanol to enhance theethanol's effectiveness.

Several patents to Swartz, U.S. Pat. No. 3,493,392, U.S. Pat. No.3,620,767, and Canadian Pat. No. 847,280, use phosphates includingsodium orthophosphate as a processing aid for fish.

Bynagte, U.S. Pat. No. 3,705,040, uses phosphates to help remove shrimpfrom their shells. Sodium orthophosphate at 2-15% with other ingredientscan be employed.

Cheng, U.S. Pat. No. 4,683,139, teaches a process for prepackaged freshmeat at retail wherein the shelf life of the meat is increased bytreatment with an aqueous solution of an alkali metal salt of certainphosphate compounds, a reducing compound such as ascorbic acid and asequestering or chelating agent such as citric acid. The phosphate canbe an orthophosphate, pyrophosphates, tripolyphosphates andhexametaphosphates. Meat pH is below neutral.

Szczesniak et al., U.S. Pat. No. 4,075,357, teaches salt combined with asecondary salt selected from alkali metal salts of organic acids andtrisodium orthophosphate, polyphosphate, metaphosphate andultraphosphate. Citrates are preferably combined with sodium chloride.These mixtures are used to control water activity in intermediatemoisture cooked food.

Kohl, et al., U.S. Pat. No. 3,681,091, teaches treating foods includingfish fillet with 10% solutions of medium chain length polyphosphates.

Freund, et al., U.S. Pat. No. 2,957,770, teaches improving theproperties of meat with a casein composition which can include inorganicorthophosphates such as disodium hydrogen orthophosphate.

Many treatment systems for poultry have been suggested. It has beenreported that the thermal death rate of salmonellae can be increasedduring scalding by elevating the pH of the scald water to pH 9.0 ±0.2.Agents such as sodium hydroxide, potassium hydroxide, sodium carbonate,and trisodium phosphate have been reported as effective pH adjustingagents for use in increasing the thermal death rate of the bacteria.Trisodium phosphate was reported as least effective in increasing thedeath rate. See "The Effect on pH Adjustment on the Microbiology ofChicken Scald-tank Water With Particular Reference to the Death Rate ofSalmonellae", T. J. Humphrey, et al., Journal of Applied Bacteriology1981, 51, pp. 517-527.

T. J. Humphrey, et al. have also reviewed the pH effect of scald wateron Salmonella on chicken skin. See "The Influence of Scald Water pH onthe Death Rates of Salmonella typhimurium and Other Bacteria Attached toChicken Skin", Journal of Applied Bacteriology 1984, 57 (2), pp.355-359. Scald water adjusted to pH 9±0.2 as in the 1981 paper can helpto reduce external and internal cross-contamination of carcasses bysalmonellas.

"Phosphate and Heat Treatments to Control Salmonella and Reduce Spoilageand Rancidity on Broiler Carcasses", J. E. Thompson, et al., PoultryScience, 1979, 58, 139-143 teach kenaphosphate a blend of 90% sodiumtripolyphosphate and 10% sodium hexametaphosphate did not consistentlyor effectively effect either salmonella survival or total bacterialcount.

Attempts have made to pasteurize poultry meat by treating the meat witha solution containing agents such as lactic acid, acetic acid, sodiumcarbonate, sodium borate, sodium chloride, potassium hydroxide, chlorineand EDTA. All treatments, except sodium borate, sodium chloride, andsodium carbonate, reduced the visual acceptability of the meat. Chlorinefailed to destroy bacteria on the surface of the poultry but would beexpected to control salmonellae in water. See Chemical Pasteurization ofPoultrv Meat, J. S. Teotia, Disseration Abstracts Int'l. B., 1974,34(a), 4142.

It is known that the shelf life of chicken carcasses can be increased 1to 2 days by chilling the poultry in a solution of 6% sodiumtripolyphosphate/0.7% tetrasodium pyrophosphate (Kena--available fromRhone-Poulenc, Inc., Food Ingredients Division). See The AntimicrobialEffect of Phosphate With Particular Reference To Food Products", L. L.Hargreaves, et al., The British Food Manufacturing Industries ResearchAssociation, Scientific and Technical Surveys, No. 76, April 1972, Pages1-20 at Page 12. Many patents and articles suggest the use ofpolyphosphates in preserving meat and fish products.

In addition, it is also stated in the Hargreaves reference at page 7that G. Pacheco and V. M. Dias in an article entitled BacteriolyticAction of Phosphates, Mems Institute Oswaldo Cruz, 52 (2) ppg. 405-414,reported on the bacteriolytic action of solutions of monosodium,disodium, trisodium and dipotassium orthophosphates on dead and livingcells of Salmonella typhosa, Escherichia coli and Staphylococcus aureus.Trisodium phosphate dodecahydrate is stated to have the greatest lyticaction. The reference does not relate to treating meat or fish.

British patent 935,413 teaches treating raw poultry in the chill tankwith a non-cyclic polyphosphate. It is taught that this method providesincreased preservation of the poultry flesh by decreasing exudate andthereby decreasing spread of bacteria.

Trisodium phosphate has also been found to be effective in inhibitingthe growth of blue mold in cuts and bruises in fruit by treating thebroken surface with the solution of trisodium phosphate (U.S. Pat. No.1,774,310).

Trisodium orthophosphate is also a known and widely used anticakingagent (see U.S. Pat. No. 2,770,548).

SUMMARY OF THE PRESENT INVENTION

In accordance with the present invention, there is provided a processfor treating red meat carcasses to remove, reduce or retard bacterialgrowth, such as salmonella, campylobacter, listeria and spoilagebacteria, without affecting the organoleptic properties of the meat. Theprocess comprises surface treating the red meat carcasses, preferablyprior to rigor, by contacting the surfaces with a solution of trialkaliorthophosphate above pH 11.5 without appreciably changing the color ofthe meat by causing a darkening of the muscle tissue resulting from highpH. By contacting the red meat prior to rigor, however, lactic acidproduced during rigor partially or totally neutralizes the trisodiumorthophosphate and further reduces any adverse pH effect on color.Alternatively, a water and/or acid wash may be employed to neutralizeany orthophosphate remaining on the surface after treatment.

The treatment is preferably conducted during slaughter either prior toor after chilling by dipping or preferably spraying the orthophosphatesolution onto all surfaces of the carcass for several minutes.Preferable treatment is done before rigor on set.

Specifically, it has been discovered that pork, beef, veal, mutton, andgoat carcasses can be treated with from about 4% to saturation of asolution of trisodium or tripotassium orthophosphate dodecahydrate or anequivalent amount of the anhydrous compound.

By use of this process the carcass can be treated economically andsimply with a food grade product to achieve salmonella and otherbacteria control without organoleptic depreciation of the carcass. Otherbenefits are evident from the description that follows.

DETAILED DESCRIPTION OF THE INVENTION

Trialkali metal phosphate is an orthophosphate salt of the formula R₃PO₄ with a formula for the sodium salt being Na₃ PO₄ and an equivalentformula for the tripotassium compounds. R is an alkali metal of sodiumor potassium. Trisodium phosphate has a minimum of 41.5% P₂ O₅ and atypical pH in a 1% solution of about 11.8.

Trisodium phosphate is available as the dodecahydrate and in commercethe dodecahydrate is available in technical or food grade. Preferablythe dodecahydrate (ether form) is used. As used herein trisodiumphosphate is intended to include tripotassium phosphate as well as allforms of those compounds.

The invention is applicable to any red meat including pork, beef, veal,mutton, lamb and goat either whole carcass or fresh parts, preferablybefore rigor and at least treated before appreciable color change isevident from the treatment.

After the animal is killed, bled, skinned and eviscerated, the carcassis normallychilled. The carcass surface is then treated with a trialkalimetal orthophosphate either before, during or after chilling. Thecarcass is treated with a treatment solution containing from about 4% tosaturation, preferably from about 6% and more preferably from about 8%to saturation of trialkali metal orthophosphate by weight of solution.From about 4% to 12%, preferably 6-12%, and most preferably from about8% to 12% orthophosphate have been effective particularly at chilledtemperature.

The carcass can be dipped in the treatment solution preferably withsolution agitation to increase contact of the treatment solution withall surfaces and crevices of the carcass. The treatment solution ispreferably applied by mechanical sprayers, usually under high pressureto insure good contact of the treatment solution with the meat surface.The treatment solution preferably contains only trialkali metalorthophosphate as the means to control, reduce, retard or removebacteria. No alcohol ,nitrate or nitrite, or ascorbic acid is employedin the treatment solution for purposes of enhancing the effect of theorthophosphate. The treatment solution may contain other ingredients forwater binding, cleaning, flavoring, coloring and the like. Salts may beused, including chlorides and the like. Normally, except in pumpingsolutions, other phosphates are not combined with the orthophosphate.

The treatment solution preferably comprised of trialkali metalorthophosphate in an amount sufficient to provide a pH above about 11.5and preferablywithin a range from 11.6 to 13.5 and most preferably fromabout pH 12 to pH 13.5.

The treatment solution is employed before, during or after eviscerationand preferably before rigor. While any temperature application ispossible, it is preferred to treat the carcass at a temperature whichdoes not cause flavor, color or appearance change usually at about thecarcass temperature. In most cases the treatment solution temperature isbelow 40° C. preferably equal to or below about 27° C. When treatingchilled meat, this temperature could be below 10° C. Preferably the redmeat is treated either before or directly after skinning and usuallyprior to chilling with a solution consisting essentially of trialkaliorthophosphate at from 4% to saturation.

The carcass surface is contacted with the treatment solution for aperiod of time sufficient to remove, retard or reduce bacterialcontamination and/or growth over and above that obtainable if pure waterwere used. Treatment dwell time is sufficient, under conditions oftreatment, to contact all contactable exposed surface of the carcass,effecting a washing of the surfaces. If desired, a layer oforthophosphate may be left on the carcass to prevent or retard furtherbacterial growth so long as significant discoloration of the carcass orresulting cut meat products is avoided.

At atmospheric pressure, in a dip tank, dwell times from 5 seconds toabout 30 minutes are effective, while dwell times using a spray rangefrom several seconds to several minutes or 2 seconds to 15 minutes withspray times of less than 30 seconds preferred.

The high pH of over 11.5 preferably about pH 12 or above is critical toremove, reduce or retard bacterial contamination or growth. Themechanism is not entirely understood, but the orthophosphate appears toimprove bacterial removal as well as retarding growth of any residualbacteria.

In a preferred embodiment of this invention, red meat is treated withtrialkali metal orthophosphate prior to pumping cuts of meat with salts,nitrate and the like. The trialkali metal phosphate treatment preventsbacteria from being driven into the meat during pumping which couldresult in later spoilage. By treating the surface first withorthophosphate any bacteria are removed or controlled prior to thepumping operation.

Immediately after treatment the meat can be processed by usual meatprocessing techniques.

If a high level of orthophosphate is present which could causediscoloration, then the red meat must be treated with water and/or adilute acid to adjust the meats pH. However, if treated before rigor,the lactic acid generated from rigor assists in controlling the browningof muscle meat.

We have found the trialkali metal orthophosphate is effective againstsalmonella, campylobactar, listeria, spoilage bacteria and the like.

EXAMPLE Carcass Preparation

A barrow was slaughtered and split in half. The right side was used asControl and the left side was treated with trisodium orthophosphate(TSP). One hour and fifteen minutes post-slaughter (pre-rigor), the leftside was totally submerged in a solution (pH 13.14) containing 10% TSPfor 2 minutes, then subsequently placed in a 38° F. cooler with thecontrol for 48 hours.

Microbioloqical Procedures

Fifteen minutes following treatment, both Control and orthophosphatecarcasses were surface swabbed at two locations at a portion of thebelly that parallel to the 10^(th) rib and an area on the carcassexterior (skin) directly opposite the 10^(th) rib sampling location.

The areas were swabbed (18 strokes) with a sterile bent glass rod. Therod was then placed in 50 ml of a phosphate buffer (pH 6.0). Onemilliliter of the 50 ml solution was then diluted in a 9 ml phosphatebuffer (pH 6.0). A total of 6 dilutions were performed. After dilution,1/10 ml was placed in a petri dish containing a pre-poured agar with 10%sheep's blood. The dishes were lncubated for 48 hours at 34° F. Totalplate counts were then conducted.

A 48 hour swabbing was also conducted in the same manner as previouslymentioned but at 5 different locations. These locations were as follows:

1. Parallel the anterior end of the aitch bone.

2. Diaphragm muscle located ventral to the 10^(th) rib.

3. Jowl region.

4. Skin of the ham opposite the aitch bone.

5. Skin of the shoulder opposite the 2nd rib.

Meat pH

A meat sample was obtained from the anterior end of the aitch bone(location 1) and the belly located ventral to the 10^(th) rib (location2). A surface pH was taken on each sample. The meat sample was thenground and a composite pH was taken.

Results

                  TABLE 1                                                         ______________________________________                                        pH of Hog Carcasses                                                                       pH                                                                Sample Location                                                                             Sample Surface                                                                            Ground Sample                                       ______________________________________                                        Control:                                                                      Ham - Anterior to                                                                           6.77        5.96                                                the aitch bone                                                                Belly - Ventral                                                                             6.58        5.72                                                the 10th rib                                                                  TSP Treated                                                                   Ham - Anterior to                                                                           6.84        5.99                                                the aitch bone                                                                Belly - Ventral                                                                             6.90        5.89                                                the 10th rib                                                                  ______________________________________                                    

Results Muscle pH

Table 1 shows that the surface pH was greater than the ground sample pHbut this difference was not greater than the 1.0 pH point at any givenlocation. The TSP treated sample pH was greater than the control forboth surface and ground sample pH readings. However, the greatest pHdifference was 0.32 between the surface Ph of the control belly and TSPbelly. These findings suggest that the little difference between thecontrol and TSP would have no effect on processing or consumerpreference.

1.5 Hours Post-Slaughter

There was no distinct visual differences between the control and the TSPtreated carcass. The TSP treated carcass did have a slightly darkerpigment color but was not that easily recognizable.

The total plate count conducted was inconclusive for both the controland TSP.

48 Hours Post-Slaughter

Visual appearance at this time period was very similar to the 1.5 hourpost-slaughter, showing little difference in muscle pigment colorbetween the control and TSP.

                  TABLE 2                                                         ______________________________________                                        Total Plate Count 48 Hours Post-Slaughter                                     Location       0 Dilution                                                     ______________________________________                                        Control:                                                                      1              18                                                             2              15                                                             3              12                                                             4              1                                                              5              5                                                              TSP Treated                                                                   1              0                                                              2              0                                                              3              0                                                              4              0                                                              5              0                                                              ______________________________________                                    

The Total Plate Count (Table 2) showed bacterial growth in thenondiluted control sample but not the TSP treated sample. The greatestgrowth was found at the aitch bone followed by the belly, jowl, shoulder(skin) and ham (skin). There was no growth recorded in the dilutions foreither the control of TSP treatment.

The Example shows a surprising lack of discoloration of a paired splithog carcass treated pre-rigor with trisodium orthophosphate.

The Example clearly shows the ability of Trisodium Phosphate to controlbacterial growth on a hog carcass without affecting the visualappearance of the lean muscle. A 10% trisodium orthophosphate solutionwas used to submerge the hog carcass for a two minute time treatmentgave a complete reduction of total plate count based on 48 hour swabbingdone at various locations on the carcass.

Trisodium phosphate either alone or in combination with other additives,with the proviso that the treatment solution of orthophosphate is freeof alcohol, nitrite or nitrates, and ascorbic acid has great potentialfor use in eliminating salmonella and other organisms red meatcarcasses.

What is claimed is:
 1. A process for treating red meat comprisingtreating the surface of eviscerated red meat, with a treatment solutioncomprising trialkali metal orthophosphate at a pH exceeding 11.5 in anamount and for a period of time effective to retard, reduce or removebacterial contamination and/or growth without substantial color changecaused by the treatment solution pH and with the proviso that thesolution does not contain alcohol, nitrate or nitrite, or ascorbic acid.2. The process as recited in claim 1 wherein said orthophosphate istrisodium orthophosphate and the amount of orthophosphate is about 4% tosaturation.
 3. The process as recited in claim 2 wherein the treatmentsolution is applied prerigor and the time of treatment is up to 30minutes.
 4. The process as recited in claim 3 wherein the treatmentsolution is sprayed on the red meat in 2 seconds to 15 minutes.
 5. Theprocess as recited in claim 1 in which the red meat is selected from thegroup consisting of pork, beef, veal, mutton, lamb and goat.
 6. Theprocess as recited in claim 1 in which the treatment solution pH rangesfrom 11.6 to about 13.5 and the solution is applied prerigor.
 7. Theprocess as recited in claim 1 in which the temperature of the solutionis equal to or less than 40 degrees C.
 8. The process as recited inclaim 1 in which the treatment solution further includes otheringredients for preservation, waterholding, cleaning, flavoring,coloring, and the like.
 9. The process as recited in claim 1 whereintreatment is conducted below 10 degrees C and is followed byconventional processing of the red meat.
 10. The process of claim 1 inwhich salmonella, campylobacter, listeria and spoilage bacteria areretarded, reduced or removed by treatment with 4% to saturation oftrisodium phosphate solution giving a pH exceeding 12.0.